Method for recovery of minerals



United States Patent j i lVIE'IHOD FOR RECOVERY 0F MINERALS Homer E.Uhland, Lakeland, Fla., assigner to International Minerals Se ChemicalCorporation, a corporation of New York Filed lune 28, 1957, Ser. No.668,801 ls claims. (ci. s- 12) This invention relates to the recovery ofcertain valuable mineral constituents from ores containing the same.More particularly, the invention relates to the recovery of metallicminerals such as ilmenite, rutile, zircon, as well as certain otherminerals from ores containing substantial amounts of phosphate rock andsiliceous material.

, The occurrence of minerals such as ilmenite (FeTiOg), Zircon (ZrSiO),and rutile (TiOz), is widespread. Up to the present time, it has beencommon practice to process or beneciate only those ores which contain arather high percentage of such valuable minerals. For example, it hasbeen found that the raw material usually must be upgraded from about 5%to about 40% by weight of such mineral in order to be amenable toflotation procedure, whereby the desired constituents of the ore arefloated away from siliceous gangue, or silica is floated away from thedesired mineral constituents. Several flotation processes have beendeveloped whereby flotation procedures have been adapted to the recoveryof these so-called heavy minerals from ores.

Traces of certain metallic minerals such as ilmenite, rutile, Zircon,sillimanite as well as minor amounts of garnet, tourmaline and monaziteare known to occur in association with silica and phosphatic rock in theFlorida phosphate field. As distinguished from their occurrence invarious Florida or Australian sands, the heavy minerals are present inthe phosphate matrix in quantities of less than about 0.1% by weight. Bysubjecting phosphate material to flotation operation for the recovery ofthe phosphatic values contained therein, according to the flotationprocesses heretofore in use, the metallic mineral content of thephosphate ore may be gathered together into a heavy mineral concentratehaving a heavy mineral content, of to 4% by'weight. ln the past, thesilica concentrates produced in the flotation of phosphatic ores havebeen discarded. This product, it has been found, contains the 2 to 4% byweight of heavy mineral as a result of treatment of the ore withcationic reagents. The composition of the silica concentrate producedVby this method averages about 60 to 70% by weight of silica, about l0 to20% by weight of tricalcium phosphate, the remainder consisting of theaforementioned heavy minerals together with other gangue impurities. Asilica fraction containing only 2 to 4% by weight of metallic mineralsis not commercially adaptable to industrial recovery processes andrequires elaborate flotation operation with consequent capitalinvestment to recover the heavy mineral in the form of a concentrateadaptable to industrial processes. lt is the primary object of thisinvention to provide a new and novel process eliminating thedisadvantages 'and shortcomings of processes heretofore in use.

It is an object of this invention to provide a novel andsimplitiedprocess-for the recovery of metallic mineral values from phosphaticores.

It is another object of this invention to provide a novel processAwhereby the. phosphate inthe concentrate is reipe covered inv higherpurity and with more complete recovery and metallic minerals recoveredin commercially acceptable concentrations.

It is still another object of this invention to provide a process whicheliminates a large number of flotation operations of the processesheretofore known.

It is still a further object of this invention to provide a processwhereby the metallic minerals are accumulated in a predominantly silicafraction which formerly was discharged to waste, and the silica fractionprocessed to recover the minerals and phosphate therefrom.

These and other objects of the invention are accomplished by subjectinga finely divided phosphatic-siliceous orewhich contains base metal oxidetype metallic minerals to at least one ilotation operation in thepresence of anionic llotation agents having an aillnity for phosphatevalue and nitrogeneous cationic agents having an affinityv for siliceousgangue, separating out a predominately siliceous fraction rich inmetallic minerals, removing the amine flotation reagent, i.e.,nitrogenous cationic agent, from said siliceous fraction, slurrying thede-reagentized siliceous material with water, separating the heavyminerals from silica and phosphate on the basis of difference ofspecific gravity and recycling the silica-phosphate fraction to theflotation system.

In carrying out the process for recovery of phosphates and heavyminerals, the phosphatic ore is subjected to a washing operation inorder to remove slime and other organic matter. The washed rock in anaqueous pulp form is subjected to screening or hydraulic sizingoperation whereby the pebble or larger particles of phosphate` rock aresegregated from material which is approximately +1 mm. size. The -l mm.size material is subjected to further Washing for complete desliming,which desliming.

tion to produce a |35 mesh size fraction which is passed to a spiral forconcentration and a -35 mesh size fraction which is the feed to theflotation circuit. The major` portion of the heavy mineral in thisphosphate material reports in this -35 +150 mesh size fraction.

In the, phosphate flotation operation, the -35 mesh fraction ofthe oreis mixed with anionic reagents which have an athnity for phosphatematerial and the heavy minerals. The reagentized mixture is subjected toflotation under conditions giving high recovery and selectivitypermitting production of a throw-away silica tail product.

Anionic or carboxyl containing negative ion agents which are useful inthe first or rougher stage of phosphate concentration, are, for example,the higher fatty acids, i.e., oleic,.stearic, and palmitic acids,natural resin acid, tall oil, naphthenic acids, alkyl sulphonated fattyacids, acid esters of high molecular weight, aliphatic alcohols and thesoaps of' such materials. Included within the term soaps of suchnegative ion or anionic type reagents are the alkali metal and alkalineearth metal soaps such as sodium, potassium, aluminum, calcium andmagnesium soaps. Soaps may also be formed by reacting such reagents withammonia or aqueous solutions thereof. The metallic mineral-containingore and phosphate having a -35 mesh particle size is reagentized withone or more of these reagents in the presence of water by agitating themixture at a solids content between about 25% and about 50% by weight,following which the slurry is diluted to a concentration suitable forintroduction into the flotation cells. In these cells a froth is formedwhich carries' the phosphate and heavy mineral to the top where thisfraction is removed by` overflow. This ore product overflowing from theanionc flotation cell is recovered for further processing as follows:The anonic reagents are removed from the solids by scrubbing withsulfuric acid; after scrubbing, the solids are washed free of reagentsand acid by agitation with wash water. The Washed solids are thenreagentized with a cationic flotation reagent designed to remove theminor component of the concentrate, i.e., silica, and the heavy mineral.Useful cationic or positive ion reagents for this stage of the flotationprocedure are the nitrogeneous positive ion agents such as the highermolecular weight aliphatic amines containing at least one alkyl grouphaving l2 to carbon atoms and their water-soluble addition salts withmineral and organic acids, esters of amino alcohol with higher molecularWeight fatty acids, and higher alkylsubstituted isoureas and theirwater-soluble salts, high molecular weight aliphatic quaternary ammoniumbases and their water-soluble salts, alkyl-substituted pyridinium andquinolineum water-soluble salts and the like.

One of the products of this cationic flotation operation is a nalphosphate concentrate which is the underflow from the flotation cells.The overflow from the cationic flotation is a mixture of silica andheavy minerals. This mixture is freed of amine reagents by any one of anumber of treatments. The mixture may be de-reagentized by treating itwith an acid material such as a mineral acid, for example, sulfuricacid; following which the acidtreated .material is washed with wateruntil it is substantially neutral. The amine reagent may also be removedby treating the slurry mixture overflowing from the cationic flotationoperation with sodium hypochlorite and the like, or chlorine water withor without subsequent washing operations. ln still another method ofcationic reagent removal, the froth slurry is mixed with slimepreviously removed in the washing of the ore. Following agitation in thepresence of the slime, the mixture is subjected to classification as ina hydroseparator to oat the slime material away from the Saud. The sandsare then washed with water and are ready for further processing. Thede-reagentized mixture of silica, phosphate, and heavy mineral is nextsubjected to separation on the basis of specific gravity differences ofthe various materials. This specific gravity separation may be effectedon the Wilfley tables but preferably is carried out in spirals where aslurry of the mixture is owed by gravity through a trough having aspiral port adapted for drop out of the heavy minerals of highestspecific gravity along the inside of trough whereas the lighter specificgravity materials continue to flow in a path .adjacent to the outerperimeter of the spiral and are recovered from the bottom of the spiral.Specific gravity differences between the heavy mineral and silica andphosphate are such that in a specific gravity separation a concentrateof heavy minerals may be produced of between 80 and 95% by Weight ofheavy mineral. The tail product from the specific gravity separationconsisting predominately of silica and phosphate, may then be recycledto the rougher flotation feed.

The metallic mineral concentrate produced in accordance with the instantnovel process is a bulk product containing all of the various heavyminerals present and may be subsequently dried and subjected to furtherconcentration by suitable means.

Reference has been made herein to rougher separation of materialstreated with anionic reagents followed by further separation of thephosphate concentrate by flotation under cationic ilotation conditionsas though these operations were performed in a single flotation stage. Asingle otation stage in each instance is the preferred embodiment of theprocess but it is not meant to exclude the possibility that each ofthese stages may be carried out in a multiplicity of stages.

The invention will be more fully understood from a study of the figurewhich illustrates the preferred embodi ment of this process. Referringto the flowsheet, deslimed phosphate ore of about -35 mesh size isindicated by the numeral Y10. Thismaterial is mixed with otation agentcomposition containing a negative lon agent such as tall oil anddelivered to flotation unit 11 from which is recovered a throw-awaysilica tail 12 and a phosphate rock concentrate 13 containing theso-called heavy mineral. The concentrate 13 is a slurry which is raisedto a solids content of about 75% at a dewatering station 14.Dewatered'concentrate is conveyed to a mixing station 15 where sulfuricacid is added to remove the anionic otation reagents. Concentrate iswashed to neutrality at washing station 16. Following washing, theconcentrate is delivered to a second flotation unit 17 where it is mixedwith a positive ion flotation agent such as a long chain aliphaticamine, and aerated and agitated to cause formation of a froth which canbe overtiowed from the flotation cell. From this flotation is recovereda phosphate concentrate or underflow fraction 18 and a silica float 19containing said heavy minerals. Silica oat 19 is conducted to adewatering station 20 and then to a de-reagentizing unit consisting of amixing station 21 where either slimes or chlorine water is added andthen to washing station 22 where water is added until the slimes orchlorine water is washed out of the slurry being treated. De-reagentizedsilica fraction is delivered from washing station 22 to a gravityseparation unit 23 where the slurry of the de-reagentizing fraction isflowed in a spiral or elliptical path. From the ports in this ellipticalpath is recovered the heavy mineral fraction 24 and the silica-phosphatefraction 25. The silica-phosphate fraction 25 is then preferablyrecycled for combining with the rougher feed.

The nature and character of the invention is further illustrated byreference to the preferred embodiment of the invention without anyintention that the invention be limited thereto.

Example A phosphate rock of the type found in phosphate pebble elds ofFlorida is subjected to a washing operation in order to remove slimesand other organic matter. The washed rock, in an aqueous pulp, issubjected to a Screening or hydraulic sizing operation whereby thelarger particles of rock are segregated from material which isapproximately -35 mesh standard screen size. The latter material is thenreagentized in an aqueous pulp containing about 60% solids with aboutone pound of a reagent cornprising about 88% tall oil and about 12%kerosene per ton of ore treated. About 2 to 4 pounds of fuel oil isadded and su'icient caustic soda is mixed into the mixture to give thelatter a pH of about 8 to 9. The resultant pulp is then subjected to aflotation operation at a solids content of about 25 to 40% by weight ina Fagergren machine and a float product is recovered containingapproximately 60% tricalcium phosphate, about 30% silica, and about 0.5%of metallic mineral. This phosphatic product is then treated with about2 pounds of sulfuric acid (60 B.) in order to remove the reagentstherefrom. The acid-treated product is washed until it is substantiallyneutral and is then reagentized in an aqueous pulp with a mixture oflong chain aliphatic amine, the latter comprising a mixture of about 73%of monooctadecyl amine and about 24% monohexadecyl amine together withsmall quantities of secondary and tertiary amines whose aliphatic groupscontain between about 12 and 18 carbon atoms. This reagent is preferablyadded in the form of acetic acid addition salt. The'reagentized productis then subjected to a flotation operation at a solids content aspreviously described. The resultant froth product from this liotationcontains a majority of the silica and about 2 to 4% by weight ofmetallic mineral. This froth product was mixed with slime materialv inproportions of approximately 5 pounds of slime solids per ton of amineflotation silica product, the slimes being the ne materialobtained fromthe hydroseparator in the washing of phosphate ore. The solids mixturewas agitated for about Zminutes and then deslimed by decantation. Thisdereagentized siliceous material is then slurried with water to adjustthe solids content of the slurry to approximately 50 to 60% by weight ofsolids and the slurry is fed through a distributor which introduces intoeach spiral about 5 tons per hours of solids. From the draw-off ports ineach spiral is recovered the bulk heavy mineral fraction and from theend of the spiral is obtained a silica-phosphate slurry.

When feeding through this process a -35 mesh phosphate feed ofapproximately 31.1% BPL, 0.4% heavy minerals, at a rate of 600 parts byweight per hou-r, a separation is made in the rougher flotation cellswhich produces a phosphate concentrate assaying about 68% BPL and 1%heavy minerals and containing about 250 parts by weight of the feed. Thethrow-away tail fraction consists of about 350 parts by weight of thefeed and assays 91% silica and about 6% BPL.

The phosphate concentrate is separated in the amine flotation cell torecover a concentrate containing about 180 parts by weight per hour anda froth flotation product containing about 70 parts by Weight per hour.The concentrate from the amine flotation will assay about 77% BPL andthe amine froth product will assay 53% silica, 38% BPL, and 7% heavymineral. In the spiral, this froth product from the amine flotation willbe separated to produce about one ton per hour of heavy mineral assaying70% heavy mineral, 19% BPL, and a tail fraction of 75 parts by weightper hour assaying 60% silica and about 30% BPL. This silica-phosphatefraction, having the same concentration of phosphate as the feed, ismixed therewith.

Having thus described the invention, what is desired to be secured byLetters Patent is:

1. A process for the recovery of base metal oxide type metallic mineralfrom phosphate-silica ores containing the metallic minerals in minoramounts which comprises subjecting the ore in a finely divided state toa flotation operation employing anionic reagents having an aflinity forphosphate to recover a phosphate-metallic mineral concentrate and athrowaway silica tail, removing the anionic reagents from said phosphateconcentrate, subjecting the phosphate concentrate after removing theanionic reagents to a flotation operation employing cationic reagents torecover a final phosphate concentrate and a silica-metallic mineralfroth product, removing said cationic reagents from said silica-metallicmineral product, diluting the silica-metallic minerals product afterremoving said cationic reagents with water, subjecting the dilutedsilica-metallic mineral product to gravitational separation therebystratifying the minerals according to their specific gravities,recovering a strata rich in metallic minerals, and recycling thesilica-phosphate strata to the feed to the anionic flotation.

2. A process for the recovery of base metal oxide type metallic mineralfrom phosphate-silica ores containing the metallic minerals in minoramounts which comprises subjecting the ore in a finely divided state toa flotation operation employing carboxy-containing negative ion agenthaving an aflinity for phosphate to recover a phosphate-metallic mineralconcentrate and a throw-away silica tail, removing thecarboxy-containing negative ion agent from said phosphate concentrate,subjecting the phosphate concentrate after removing thecarboxycontaining negative ion agent to a flotation operation employingnitrogenous positive ion agent to recover a final phosphate concentrateand a silica-metallic mineral froth product, removing said nitrogenouspositive ion agents from said silica-metallic mineral product, dilutingthe silica-metallic minerals product after removing said nitrogenouspositive ion agent with Water, subjecting the diluted silica-metallicmineral product to gravitational separation thereby stratifying theminerals accord ing to their specific gravities, recovering a stratarich in metallic minerals and recycling the silica-phosphate strata tothe feed to the carboxy-containing negative ion agent flotation.

3. A process for the recovery of base metal oxide type metallic mineralfrom phosphate-silica ores containing the metallic minerals in minoramounts which comprises subjecting the ore in a finely divided state toa flotation operation employing anionic reagents having an aflinity forphosphate to recover a phosphate-metallic mineral concentrate and athrow-away silica tail, removing the anionic reagents from saidphosphate concentrate, subjecting the phosphate concentrate after thereV moval of said anionic reagents to a flotation operation employingcationic reagents to recover a final phosphate concentrate and asilica-metallic mineral froth product,

removing said cationic reagents from said silica-metallic mineralproduct, diluting the silica-metallic minerals product after the removalof said cationic reagents with water, subjecting the dilutedsilica-metallic mineral product to spiral separation thereby stratifyingthe minerals according to their specific gravities, recovering a stratarich in metallic minerals, and recycling the silica-phosphate strata tothe feed to the anionic flotation.

4. A process for the recovery of base metal oxide type metallic mineralfrom phosphate-silica ores containing the metallic minerals in minoramounts which comprises subjecting the ore in a finely divided state toa flotation operation at a pH in the range between about 8 and 9,employing carboxy-containing negative ion agent having an affinity forphosphate to recover a phosphate-metallic mineral concentrate and athrow-away silica tail, removing the carboxy-containing negative ionagent from said phosphate concentrate, subjecting the phosphateconcentrate after the removal lof carboxy-containing negative ion agentto a flotation operation employing nitrogenous positive ion agent torecover a final phosphate concentrate and a silica-metallic mineralfroth product, removing nitrogenous positive ion agents from saidsilica-metallic mineral product, diluting the silica-metallic mineralsproduct after the removal of said nitrogenous positive ion agent withwater, subjecting the diluted silica-metallic mineral product togravitational separation thereby stratifying the minerals according totheir specific gravities, recovering a strata rich in metallic mineralsand recycling the silica-phosphate strata to the feed to thecarboxycontaining negative ion agent flotation.

5. A process for the recovery of base metal oxide type metallic mineralfrom phosphate-silica ores containing the metallic minerals in minoramounts which comprises subjecting the ore in a finely divided sta-te toa flotation operation employing anionic reagents having an affinity forphosphate to recover a phosphate-metallic mineral concentrate and athrow-away silica tail, removing the anionic reagents from saidphosphate concentrate by adding sulfuric acid to a slurry of saidconcentrate and agitating the mixture, washing the concentrate to a substantially neutral pH, subjecting the phosphate concentrate afterwashing to a flotation operation employing cationic reagents to recovera final phosphate concentrate and a silica-metallic mineral frothproduct, removing cationic reagents from said silica-metallic mineralproduct, diluting the silica-metallic minerals product with water,subjecting the diluted silica-metallic mineral product to gravitationalseparation thereby stratfying the minerals according to their specificgravities, recovering a strata rich in metallic minerals, and recyclingthe silicaphosphate strata to the feed to the anionic flotation.

References Cited in the file of this patent UNITED STATES PATENTS LawverOct. 21, 1952 Duke et al. July 10, 1956 OTHER REFERENCES

1. A PROCESS FOR THE RECOVERY OF BASE METAL OXIDE TYPE METALLIC MINERALFROM PHOSPHATE-SILICA ORES CONTAINING THE METALLIC MINERALS IN MINORAMOUNTS WHICH COMPRISES SUBJECTING THE ORE IN A FINELY DIVIDED STATE TOA FLOTATION OPERATING EM PLOYING ANIONIC REAGENTS HAVING AN AFFINITY FORPHOSPHATE OT RECOVER A PHOSPHATE-METALLIC MINERAL CONCENTRATE AND ATHROWAWAY SILICA TAIL,REMOVING THE ANIONIC REGENTS FROM SAID PHOSPHATECONCENTRATE, SUBJECTING THE PHOSPHATE CONCENTRAATE AFTER REMOVING THEANIONIC REGENTS TO A FLOTATION OPERATION EMPLOYING CATIOMIC REGENTS TORECOVER A FINAL PHOSPHATE CONCENTRATE AND A SILICA-METALLIC MINERALFORTH PRODUCT, REMOVING SAID CATIONIC REGENTS FROM SAID SILICA-METALLICMINERAL PRODUCT, DULUTING THE SILICA-METALLIC MINERALS PRODUCT AFTERREMOVING SAID CATIONIC REGENTS WITH WATER, SUBJECTING THE DILUTESILICA-METALLIC MINERAL PRODUCT TO GRAVITATIONAL SEPARATION THEREBYSTRATIFYING THE MINERALS ACCORDING TO THEIR SPECIFIC GRAVITIES,RECOVERING A STATA RICH IN METALLIC MINERALS, AND RECYCLING THESILICA-PHOSPHATE STRATA TO THE FEED TO THE ANIONIC FLOTATION.